I never thought I could tell the difference, but I was playing the Battlefront Beta (60 fps) and then switched back to Destiny (30 fps) and it was super obvious. The game seemed stuttery, but I got used to it after a while.
Platinums: Red Dead Redemption, Killzone 2, LittleBigPlanet, Terminator Salvation, Uncharted 1, inFamous Second Son, Rocket League